Some doors of this type are exposed to the action of the wind. Various means are known for preventing major deformation which could damage the door or jam it. The vertical edges of the curtain may have a portion of greater thickness or skids fixed thereon for sliding in a channel (like sails on a boat). Vertically spaced-apart horizontal reinforcing bars are also used with their ends sliding in slideways. The invention relates, in particular, to a lifting curtain door comprising a frame constituted by two vertical side uprights interconnected at the top by a cross-member, each of the said side uprights comprising or including a slideway with each slideway having a guide wall on either side of the plane of the curtain with the curtain being gathered together at the top by rolling up or by folding, the curtain being reinforced by horizontal bars whose ends slide in the said slideways.
These various systems suffer from the drawback that during various kinds of traffic accident, when a vehicle strikes the door before the door is fully opened, the door is damaged. Indeed the door is often jammed and it is necessary to dismount the door. Traffic is interrupted and repairs may be expensive, the curtain may be torn; a twisted bar may need extracting; etc.
The Applicant has already proposed a reinforcing bar device in which the ends sliding in the slideways include a section of weakness. As a result, when there is a shock against the bar, it breaks at the end and the door can still be operated. There is merely the end of one of the bars that is no longer guided and this is easily repaired by replacing the broken part.
Although the above system is advantageous in many applications, it is not suitable for all applications, and a certain amount of time must nevertheless be allowed for performing repairs.
The object of the present invention is to avoid the door being damaged when a vehicle strikes against the curtain before it is fully opened, or when excessive wind force is applied thereto, so that under the effect of such a shock, the door, or at least one of the door components, is subjected to nonpermanent deformation, thereby enabling the door to return to its proper position merely by being operated and without any other action being taken.